1. Field of the Invention
The present invention relates to a nut member, more particularly to a nut member with tightness-indicating protrusions and loosening-preventing recesses.
2. Description of the Related Art
U.S. Pat. No. 3,194,105 discloses a conventional nut body that has a square base provided on its underside with a relieved octagonal recess, four grooves across four corners of the nut body which are provided with four triangular feet, and a gap on each side of the base between two adjacent ones of the triangular feet. The gaps on the sides of the base are utilized to indicate when the desired minimum tension has been achieved in a bolt applied with the nut body.
U.S. Pat. No. 2,570,863 discloses a conventional nut body that has a flat thrust face which is provided with parallel symmetrically disposed ridges. Parallel slots are formed in the nut body, and are spaced apart from and are aligned with the ridges. As the nut is tensioned on a bolt, the ridges are forced in an axial direction and are moved toward the nut axis to close the initially open sides of the slots.
The aforementioned conventional nut bodies are disadvantageous in that loosening of the conventional nut body on the bolt tends to occur due to repeated expansion and contraction of the nut body and the bolt.